Given the immensity of the territory involved, it's a safe bet that only a small fraction of the perps are getting caught
The biggest "perp" out there is mother nature. Some fires are started by arsonists, there is no doubt about that, but the majority are caused by lightning strikes. It is a perfectly normal function of the ecosystem, most of the time.
What is not "normal" is fire suppression activities and on a broader scale, forest management objectives. Climatic changes are also an immense factor. A lot of timber out there (almost all of it) is seen as standing money by some interests - mainly those who control what happens with that timber. When it is going up in smoke, crews are sent in to put out the fires and secure the timber supply. It is literally money going up in smoke. Not to mention communities, livelihoods, etc.
In a distant lifetime now, I used to be one of those crew members. I would regularly get dropped off by a helicopter in a patch of forest in the middle of nowhere with pumps, hand tools, a little bit of food and a whole lot of hose to put them out. It cost the tax payer many millions. Made good money that put me through university though! The only reason I was there 95% of the time was to protect timber supply. Community protection or special interest protection of structures was very rare.
However, this long, long history of fire suppression has the knock-on effect of increasing fuel loads, leading to ever bigger and more intense fires. Compounded with things like drought, and well, good luck.
We're starting to see the impact of that now. In the past, the massive campaigns ala "smokey the bear" were very popular. Some people of a generation may remember that. It had a much bigger impact on the collective psyche than many realize. Slowly, forest management is moving away from this mindset, but we will be dealing with the effects for a long time.
As with anything, the story is often complicated. Imagine how someone who is not a pipe smoker views restoring a pipe. "So what? You file this bit a little, polish that and bam, there's your pipe." Easy-peasy, and you could hardly call it "woodwork". Or so the impression is.
But we know it is not that simple. Looking to other areas where people have a very long history in studying and working with issues of any kind, it is exactly the same. It is far more complex than it seems.
It's a very unfortunate perfect storm. It has been happening with more frequency. This has been obvious to a lot of so called "experts" for some time now, but it is only recently where it has been coming home to roost on the doorsteps of a lot more people who were otherwise blissfully unaware or uninterested.